Re: [AUDITORY] Seeking advice on using ANF firing rate to reslove front-back confusion in sound localization model

[Qin Liu <000003c563e12bd3-dmarc-request@xxxxxxxxxxxxxxx>]

Dear Dick,

Thank you for your suggestions.

I am a little confused about the concept of "rate-vs-place profiles." Could you please provide more references or explain it a bit more? I believe spectral cues will definitely help, but I haven't found a proper way to manipulate them yet.

I've attempted to use head rotation to determine whether the sound source is from the front or back based on the MSO firing rate, which requires turning +/- 90 degrees each time. This is why I am seeking alternative methods to address this issue.

Best regards,

Qin

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From: Richard F. Lyon <dicklyon@xxxxxxx>
Sent: Thursday, 27 February 2025 12:08:01
To: Qin Liu
Cc: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: Seeking advice on using ANF firing rate to reslove front-back confusion in sound localization model

 

Qin,

The rate-vs-place profiles from the two ears may have most of what you need to supplement the MSO's output that represents ITD, which is mostly a left-right cue.  The cues for elevation, including front-back, are generally thought to be more subtle spectral features, related to the individual's HRTF, and are not as robust as the ITD cues.  ILD cues are of intermediate robustness, I think, but still primarily left-right.

I hadn't thought about doing what Jan Schnupp suggested, looking at slightly different cones of confusion for different frequencies, but that sounds like another way to conceptualize the subtle HRTF-dependent spectral cues.

So you don't have to use "HRTF template matching", but you do have to use HRTFs.

If you want to do this in anything like the real world, as opposed to an anechoic environment, you'll need a strong precedence effect to pay attention to the first arrival and ignore echos, or something along those lines. 

Also, in the real world, we usually resolve front-back confusion quickly and easily by rotating our heads a little.  The effect of rotation on ITD is opposite for front vs back, so this gives a very robust front-back cue; up-down is still hard.

Dick

On Wed, Feb 26, 2025 at 4:21 PM Qin Liu <000003c563e12bd3-dmarc-request@xxxxxxxxxxxxxxx> wrote:

Dear auditory list,

I am currently working on a project involving sound localization using firing rates from auditory nerve fibers (ANFs) and the medial superior olive (MSO). However, I have encountered an issue: I am unable to distinguish between front and back sound sources using MSO firing rates alone but only the left-right.

I am considering whether auditory nerve fiber (ANF) firing rates might provide a solution, but I am uncertain how to utilize them effectively. For instance, I have experimented with analyzing the positive gradients of ANF firing rates but have not yet achieved meaningful results.

Could anyone suggest an auditory metric derived from binaural signals, ANF firing rates, or MSO that could classify front/back sources without relying on HRTF template matching? Any insights or alternative approaches would be invaluable to my work.

Thank you in advance. I sincerely appreciate any guidance you can offer.

Best regards,

Qin Liu
Doctoral Student
Laboratory of Wave Engineering, École Polytechnique Fédérale de Lausanne (EPFL)
Email: qin.liu@xxxxxxx